diff --git a/NEWS.md b/NEWS.md
index 71228d4b..1e3b17eb 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # scales (development version)
 
+* `train_continuous()` coerces `new` to numeric before calculating range 
+  (@teunbrand, #369).
+
 # scales 1.2.1
 
 * Re-document to fix HTML issues in `.Rd`.
diff --git a/R/scale-continuous.R b/R/scale-continuous.R
index 8ad1cfb1..a26334ae 100644
--- a/R/scale-continuous.R
+++ b/R/scale-continuous.R
@@ -46,7 +46,10 @@ train_continuous <- function(new, existing = NULL) {
     cli::cli_abort("Discrete value supplied to a continuous scale")
   }
 
-  suppressWarnings(range(existing, new, na.rm = TRUE, finite = TRUE))
+  # Needs casting to numeric because some `new` vectors can misbehave when
+  # combined with a NULL `existing` (#369)
+  suppressWarnings(range(existing, as.numeric(new),
+                         na.rm = TRUE, finite = TRUE))
 }
 
 # Map values for a continuous palette.
diff --git a/tests/testthat/test-scale-continuous.R b/tests/testthat/test-scale-continuous.R
index fd81e4f2..8c8e3074 100644
--- a/tests/testthat/test-scale-continuous.R
+++ b/tests/testthat/test-scale-continuous.R
@@ -27,3 +27,12 @@ test_that("train_continuous with new=NULL maintains existing range.", {
     c(1, 5)
   )
 })
+
+test_that("train_continuous works with integer64", {
+  skip_if_not_installed("bit64")
+  new <- bit64::as.integer64(1:10)
+  expect_identical(
+    train_continuous(new),
+    c(1, 10)
+  )
+})